Mechanical and electro-mechanical systems (such as gas turbine engines) may comprise one or more objects (such as discs, drums, cover plates and turbine blade tips) having abrasive surface coatings for clearance control purposes. The abrasive surface coatings may be applied according to fine positional and compositional tolerances. Where an abrasive surface coating on an object is outside of those tolerances, the performance and/or efficiency of the mechanical or electro-mechanical system may be adversely affected. For example, where an abrasive surface coating on a seal fin within a gas turbine engine is outside of predetermined tolerances, the seal fin may allow gas to leak there through which may affect the performance and/or efficiency of the gas turbine engine.